body{
    display: flex;
    flex-direction: column;
    
    // 详情
    .datail{
        flex-grow: 1;
        position: relative;
        
        // 视频预览
        .video-box{
            width: 100%;
            height: 300px;
            // background-color: #000;

        }

        // 返回上一级箭头
        .lt{
            position: absolute;
            left: 20px;
            top: 20px;
            width: 30px;
            height: 30px;
            padding: 10px;
            font-family: 宋体;
            font-weight: 900;
            background-color: #fff;
            border-radius: 50px;
            text-align: center;
            line-height: 12px;
        }
    }

    // 开始训练按钮
    .start-btn{
        padding: 20px;
        
        #btn{
            display: block;
            margin: 0px auto;
            width: 100%;
            height: 40px;
            line-height: 40px;
            background-color: #4294ff;
            text-align: center;
            border-radius: 20px;
            color: #fff;
        }
    }
}